Riveting in Sheet Metal Fabrication(mig vs tig welding Tiffany)

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Rivets are a common and effective way to join and fasten pieces of sheet metal together. They create a permanent mechanical attachment that is strong, reliable, and suitable for many applications. Here is an overview of riveting in sheet metal fabrication.
What is a Rivet?
A rivet is a mechanical fastener that consists of two main parts - a smooth cylindrical shaft and a head. The rivet is inserted through holes drilled or punched into the sheets being joined. The protruding end is then upset, or bucked, to form the second head. This creates a permanent joint.
Rivets are available in many materials, sizes, and styles to suit different fabrication needs. Common materials include aluminium, steel, copper, stainless steel, and Monel. They may have round, oval, flat, or countersunk heads. Rivet diameters range from 1/16 inch to 1/4 inch. Lengths range from 1/8 inch to several inches.
Benefits of Riveting
Riveting offers many benefits for joining sheet metal:
- Strong and permanent - Properly installed rivets create a tight joint that does not loosen over time. The upset head anchors the rivet securely in place.
- Vibration resistant - Riveted joints can withstand vibration and shock better than many mechanical fasteners. Rivets are commonly used in aircraft and other high vibration applications.
- Leakproof - The compression and deformation of the rivet shank creates a tight seal around the hole. This helps prevent leakage in plumbing, chemical processing, and storage vessels.
- Low profile - Countersunk rivets allow flush mounting. This results in minimal disruption to air flow and aesthetics.
- Quick installation - Riveting is generally faster than welding or screwing. It takes less skill to operate riveting tools effectively.
- Thermal and electrical conductivity - Choosing rivets of the appropriate metal allows heat and electrical current to pass through the joint. Copper and aluminium rivets excel here.

Riveted Joint Design
Proper design is key to creating strong, long-lasting riveted sheet metal joints. Here are some best practices:
- Hole size - Holes should match the rivet diameter closely, generally within a few thousandths of an inch. Loose holes reduce strength. Excessively tight holes make insertion difficult.
- Hole spacing - Spacing holes too closely together weakens the joint. As a rule of thumb, separate rivets by at least three times the rivet diameter. Closer spacing requires engineering analysis.
- Edge distance - Provide sufficient distance between rivets and sheet edges, at least 1.5 times the rivet diameter. This prevents edge tear out.
- Row spacing - Space parallel rows of rivets far enough apart to maintain strength. Aim for four times the rivet diameter between rows.
- Rivet pattern - Staggering rivets in zigzag or diamond patterns distributes load most evenly. Inline patterns are acceptable for light loads.
- Rivet length - Rivet length should be 1.5 to 2 times the combined thickness of the sheets. This provides enough shank to form a second upset head.
- Rivet strength - Select rivets strong enough to meet the design loads. Consider shear strength, tensile strength, and material properties.
Riveting Equipment
Installing rivets properly requires the right tools. Here are the main pieces of equipment used:
- Riveting hammers - These hammer heads have a cupped shape to form the rivet head. Variations exist for different rivet styles and materials.
- Bucking bars - Bars with flat or shaped ends are placed against the back side sheet. The riveter hammers the front side head, while the bucker absorbs the impact.
- Rivet guns - Pneumatic, hydraulic, or electric rivet guns pull the rivet set into the workpiece, upsetting the tail. This replaces hammering.
- Rivet sets - A set and die shape the rivet head appropriately for the intended style and head profile.
- Hole punches - Manual and powered hole punches cut or punch rivet holes quickly and accurately. Good for mass production.
- Drills - twist drills make holes in sheet metal for rivets. CNC machines automate drilling for large jobs.
- Countersinks - These cutters bevel holes to recess rivet heads. Necessary for flush mounting rivets.

The Riveting Process
Skilled technicians can rivet sheet metal by hand using simple hammers and bucking bars. But most fabrication shops use power tools to increase speed and efficiency. Here are the basic steps for machine riveting:
1. Shear or punch rivet holes to size. Deburr edges and remove sharp shards that could cut rivet shank.
2. Clamp components to be joined in alignment. Fixtures help hold alignment during riveting.
3. Insert rivet through holes with protruding shank on accessible side.
4. Position bucking bar against shop head side. Place rivet set in gun against shank.
5. Squeeze rivet gun trigger to upset shop head. Release once formed.
6. Repeat staking with bucking bar and set to work-harden shop head and improve head shape.
7. Flip assembly and upset the bucktail head with rivet set. Repeat staking.
8. Inspect rivets visually and with taps from a light hammer. Replace underset or cracked rivets.
9. If necessary, use a countersink tool to create flush mount rivet heads. Grind any remaining unevenness.
10. Remove clamps and complete post-rivet installation processing and finishing.
Riveting is an efficient, affordable, and time-tested method for fastening sheet metal. With care and expertise, riveted assemblies can provide many years of reliable service across countless applications. Proper joint design, equipment selection, and installation practices are key to success. CNC Milling